In this study, a simple two-dimensional measurement system based on optical design was developed to measure the motion errors of the linear guideway. Compared with the transitional methods about the linear guideway for measuring the motion errors, our proposed two-dimensional optical measurement system can simultaneously measure horizontal and vertical running straightness errors for the linear guideway. Calibration results showed that the residual error of the two-dimensional optical measurement system is less than 0.5 µm. Measurement results showed that the three tests for the motion errors of the linear guideway are almost coincident with the laser interferometer within 1000 mm. The standard deviations of the horizontal and vertical straightness measurement systems are 0.9 and 1.2 µm.